Use GET parameter as Insert Record trigger?

I'm converting all my old captcha widgets to use Google's reCaptcha instead. It works fine when using email behaviors, however I have a few registration forms which insert a record in the database and also send an email. I don't think I can apply WA server validation to the reCaptcha widget as it's just a div (i.e. <div class="g-recaptcha" data-sitekey="xxxxxxx"></div>, however this means that when the Submit button is pressed (the trigger for inserting the record and sending the email), the email won't send but the record is being written to the database as long as all the other validations are passed. I thought a way around this may be to use a GET parameter as the Insert Record trigger instead of the usual Submit button pressed option, i.e.:

// WA DataAssist Insert
if ((isset($_GET["sent"]) && $_GET["sent"] == "true")) // Trigger

It did write a record to the database but didn't post the info from the form! Am I missing something here, or is there another way I could add reCaptcha to the WA Server Validations?